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Herbivory is of extreme ecological importance and prevalence among insects.Perhaps one third (or 500,000) of all described species are herbivores. [4] Herbivorous insects are by far the most important animal pollinators, and constitute significant prey items for predatory animals, as well as acting as major parasites and predators of plants; parasitic species often induce the formation of galls.
Herbivores are dependent on plants for food, and have coevolved mechanisms to obtain this food despite the evolution of a diverse arsenal of plant defenses against herbivory. Herbivore adaptations to plant defense have been likened to "offensive traits" and consist of those traits that allow for increased feeding and use of a host. [1]
An old castaway hut on the Antipodes Islands.. The islands constituting this ecoregion share a long history of isolation, both from other landmasses and each other. The isolation, combined with harsh climates characterised by low temperatures, strong westerly winds and few hours of sunlight in winter, have resulted in the evolution of many endemic plants and animals, though species richness is ...
According to the theory of predator–prey interactions, the relationship between herbivores and plants is cyclic. [62] When prey (plants) are numerous their predators (herbivores) increase in numbers, reducing the prey population, which in turn causes predator number to decline. [62] The prey population eventually recovers, starting a new cycle.
The flora of the alpine tundra is characterized by plants that grow close to the ground, including perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. [28] The flora is adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season.
At higher altitudes, the terrain is arctic tundra. Svalbard has permafrost and tundra, with both low, middle and high Arctic vegetation. 165 species of plants have been found on the archipelago. [9] Only those areas which defrost in the summer have vegetation cover and this accounts for about 10% of the island group.
These complex interactions between plants, animals and abiotic factors in the tundra are held together by the permafrost layer, located 450 metres (1,480 ft) under the soil. [3] However climate change is causing this crucial layer of frozen soil to melt. As a result, tundra communities are becoming unstable and basic processes are breaking down.
These rocky islands support a variety of plant life, such as tussock grasses, that has adapted to the snowy and icy conditions.There are a number of endemic plant species including Poa cookii grass and the Kerguelen cabbage (Pringlea antiscorbutica), historically a source of vitamin C for sailors, is found on all the islands, not only the Kerguelens.